In many communication applications, a transmitter transmits signals to a receiver over a communication channel, and the receiver estimates the response of the communication channel. Channel estimation can be used for various purposes, such as for channel equalization or other reception tasks, or for sending feedback to the transmitter so as to adapt subsequent transmissions to the channel conditions. In some communication systems, the receiver estimates the channel by processing reference signals or pilot signals that are transmitted from the transmitter.
Channel estimation based on reference signals is used, for example, in Evolved Universal Terrestrial Radio Access (E-UTRA) systems, also referred to as Long Term Evolution (LTE) systems. Reference signals and channel estimation in LTE systems are specified by the Third Generation Partnership Project (3GPP), in “Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8),” TS 36.211, version 8.8.0, September, 2009, section 6.10, which is incorporated herein by reference.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.